The present invention relates to a laminated electric double layer capacitor module, particularly to a laminated electric double layer capacitor module having a high output density and a high energy density per volume or per weight.
An electric double layer capacitor is excellent in the output density or the long-term reliability for charge/discharge cycles, and it is being employed as a power source for a hybrid electric car or as an emergency electric power source. In such a power source application, a high voltage at a level of a few hundreds V is required.
Usually, the operating voltage of a unit cell of an electric double layer capacitor is from 0.6 to 0.8 V in a case where the electrolyte is an aqueous solution type, or from 2.0 to 3.3 V in a case where the electrolyte is a non-aqueous solution type. Accordingly, such unit cells are used in the form of a high voltage power source module in which from a few tens to a few hundreds of such unit cells are connected in series.
As the structure of such a unit cell, a prismatic cell or a cylindrical cell is common. A prismatic cell is as shown in FIG. 8 i.e. a plurality of flat plate positive and negative electrodes 7A and 7B are alternately stacked with a separator 2 interposed in-between to form multilayer element assembly, and the assembly is accommodated in a prismatic case 11. From the respective electrodes 7A and 7B, flat plate leads 8A and 8B extend upwardly and bundled, respectively, at lead joint portions 9A and 9B as divided into positive electrodes and negative electrodes. The lead joint portions 9A and 9B are connected and secured to positive and negative terminals 10A and 10B, respectively, which are secured as passed through the prismatic case 11.
A cylindrical cell is as shown in FIG. 9 i.e. a pair of long strip-shaped positive and negative electrodes 1A and 1B and a separator 13 interposed therebetween, are wound up to form a winding element, and this winding element is accommodated in a cylindrical case 15 to form a cylindrical cell.
Leads 5A and 5B are connected to the upper ends of the positive and negative electrodes 1A and 1B, respectively. These leads 5A and 5B are connected to the positive and negative electrode terminals 4A and 4B, respectively, which are secured as passed through a sealing insulating plate 3. For example, as shown in FIG. 10, a plurality of unit cells 20 thus constructed, are connected in series to constitute a high voltage power source module.
However, in order to integrally secure the plurality of unit cells 20, strongly-built module structural members 21 are required, and in order to electrically connect the unit cells 20 in series, many connecting bus bar members 23 are required.
Accordingly, after finishing into a high voltage power source module, the weight increase and the volume increase required to form the module, are substantial, and as the high voltage power source module as a whole, the output density and the energy density deteriorate substantially. Namely, there has been a problem that the high output density as a merit of an electrical double layer capacitor is lost, and the low energy density becomes distinct.
The present invention has been made in view of such problems of the prior art, and it is an object of the present invention to provide a laminated electric double layer capacitor module having a high output density and a high energy density per volume or per weight.
The present invention provides a laminated electric double layer capacitor module comprising:
electrode assemblies for positive and negative electrodes disposed to face each other, each comprising a metal current collector foil and an electrode layer made of a large surface area material, formed on at least one surface of the foil except for an end strip portion along one side end of the foil;
an ion permeable separator disposed between the adjacent electrode assemblies to separate the respective electrode layers from each other;
a metal current collector plate for positive electrodes and a metal current collector plate for negative electrodes, electrically connected to the end strip portion of each electrode assembly for positive electrode and the end strip portion of each electrode assembly for negative electrode, respectively;
an electrolyte; and
a module case; wherein:
a) the electrode assemblies for positive and negative electrodes are alternately laminated in plurality so that the respective end strip portions are projected from the separators on opposite sides, to form a laminated element;
b) the metal current collector plate for positive electrodes, is disposed at the end of the laminated element on the side where the end strip portions of the metal current collector foils for positive electrodes are projected from the separators;
c) the metal current collector plate for negative electrodes, is disposed at the end of the laminated element on the side where the end strip portions of the metal current collector foils for negative electrodes are projected from the separators;
d) the electrode assemblies, the separators, the current collector plate for positive electrodes and the current collector plate for negative electrodes, are integrated to constitute a laminated element assembly;
e) a plurality of such laminated element assemblies are provided, and each of them is accommodated and protected in one of element compartments formed in plurality in the module case; and
f) the plurality of the laminated element assemblies accommodated in the plurality of the element compartments, respectively, are electrically connected in series.
The module of the present invention does not require to employ strongly-built module structural members to integrally secure the plurality of cells or many electrical connecting members for cells, which used to be required to construct a high voltage power source module by connecting unit cells in series. According to the present invention, it is possible to increase the energy density per volume or per weight, as a module power source. Especially when a resin case lighter than a metal, is used as the module case, the energy density can further be increased. Further, the process until a final laminated module power source is prepared, can be simplified, and the number of components required, is small, whereby the productivity is excellent, and the production cost can be reduced.
In the present invention, it is preferred that the module case comprises a module case main body provided with said element compartments, and a module case cover to close the module case main body.
By this construction, the module case is constituted by the module case main body and the module case cover, whereby the production is easy, and the repair services, etc., are easy.
Further, in the present invention, it is preferred that a connecting means is provided which is connected to the current collector plate for positive electrodes and/or the current collector plate for negative electrodes through a partition wall partitioning the adjacent element compartments of the module case main body or through both side walls of the module case main body.
Thus, by using some components constituting the case for unit cells in common to construct a structure comprising module-constituting members and electrical connecting members between cells, it is possible to obtain a laminated electric double layer capacity module which is more compact and lighter in weight.
Further, the adjacent unit cells can be connected in the minimum distance without requiring bus bars or the like, whereby the resistance as a module power source can be made lower than before.